This invention relates generally to dental hygiene systems and methods for enhancing the toothbrushing process. More particularly this invention relates to a dental hygiene system and method in which UVA light is delivered, by way of a specially adapted toothbrush or other device, directly to a photocatalyst deposited on the teeth, gums, tongue, and on other structures found in the mouth. The dental hygiene system and method, which delivers the UVA light from a source contiguous to the head of the toothbrush or other device, efficiently oxidizes and destroys potentially problematic bacteria or odorous compounds in the mouth. The potentially problematic bacteria and other organic species are associated with, for example, tooth decay, gum disease, denture stomatitis and halitosis/malodor. The dental hygiene system and method also whiten the teeth by oxidizing stains. This invention can also be used for the disinfection of dentures inside or outside of the mouth. Finally, as a part of the overall system and method, this dental hygiene system and method also disinfects key areas of the toothbrush or other device used to deliver the UVA light.
The use of photocatalysis in purifying both gas and liquid media and in controlling bacteria and other microorganisms on the surfaces of solid objects is a relatively new and rapidly growing technology. This photocatalysis process entails the illumination of catalytic n-type semiconductor particles (such as TiO2 particles) with UVA light. It is believed that the UVA light promotes photoexcitation of valence band electrons and holes in the semiconductor particles, and that the electrons and holes migrate to the surface of the semiconductor particles to participate in reduction/oxidation reactions with matter adsorbed to or in the near vicinity of the surface of the particles. It is further believed that these reduction/oxidation reactions produce highly reactive hydroxyl radicals which oxidize and ultimately destroy certain organic species in the gas or liquid media, or on the semiconductor-bearing surfaces being treated.
The use of photocatalysis of certain organic compounds and dyes, and of catalytic n-type semiconductor particles in promoting dental hygiene is known to a limited extent. More particularly, U.S. Pat. No. 6,343,400 to Massholder describes a photocatalytic cleaning method for destroying bacteria on teeth and gums, whitening the teeth, and removing other organic impurities in the mouth. This method employs a toothbrush as a light guide to deliver UVA light to the mouth. The toothbrush includes a brush in its distal end in which at least some bristles are optical fibers. Just as in conventional toothbrushes, the bristles mechanically remove plaque from the teeth as they are brushed. As the brushing proceeds, the optical fiber bristles guide UVA light from the grip area at the proximal end of the instrument onto the tooth and gum surfaces where, together with a catalytic semiconductor, oxidative cleaning is produced by way of the photocatalysis process discussed above. As Massholder explains, the combination of mechanical cleaning with the UVA-light-induced oxidation increases the effectiveness of the brush, particularly with regard to the control of certain germs. Also, the bristles displace the semiconductor repeatedly from one point to another to further enhance the oxidation process.
Massholder's prior art instrument for delivering UVA light to the mouth is illustrated in FIG. 1. This device comprises a toothbrush 4 at its distal end with a handle 6 containing a UVA light source 7 at its distal end. The UVA light source generates UVA light with a wavelength in the range of 320 to 400 nm. The UVA light is guided to the brush head 4 via a light guide 9 comprising a number of light-guiding fibers positioned in the stem 8 of the toothbrush. A reflector 10 is also provided to direct the UVA light into the entrance of the light guide 9.
Since the period of irradiation of the catalyst in any particular location in the mouth is very short during the toothbrushing process, and significant attenuation of the radiation strength occurs in its transmission within any optical fibers, it would be highly desirable to be able to provide a way of safely intensifying the effectively delivered UVA light by delivering the UVA light directly from the light source to the semi-conductor particles. This would eliminate the fall-off of the intensity of the initial UVA light by eliminating absorption in the fibers and hence accelerate the oxidation process, thereby maximizing the effectiveness of the overall system.